Cleaned up FIXME notes and various small things in jbpm-bpmn2 (and jbpm-flow-builder) tests
JBPM-3785 (Compensation): making sure all nodes have unique id's
JBPM-3785 (Compensation): jbpm-bpmn2 tests

- including tests for nested event sub processes
JBPM-3785 (Compensation): serialization/protobuf logic for the WorkflowProcessInstanceImpl.completedNodeIds field
Fixed mistake in Chapter-ExceptionMgmt.xml
JBPM-3785 (Compensation): corrected the BroadcastEventTypeFilter (docs and func)